Add render error logging for debugging

server/drone_forest_environment.py

@@ -468,7 +468,10 @@ class DroneForestEnvironment(Environment):
             buf = io.BytesIO()
             img.save(buf, format="PNG")
             return base64.b64encode(buf.getvalue()).decode("utf-8")
-        except Exception:
+        except Exception as e:
+            import traceback
+            print(f"[render error] {e}")
+            traceback.print_exc()
             return None
 
     @property